Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness

by Peter Godfrey-Smith

The chemistry of life is an aquatic chemistry. We can get by on land only by carrying a huge amount of salt water around with us.

The transition to a multicellular form of life occurred many times, leading once to animals, once to plants, on other occasions to fungi, various seaweeds, and less conspicuous organisms.

The biologist Andrew Parker has argued that the invention of eyes was the decisive event in the Cambrian.

Near the close of the Ediacaran, Gehling suspects that scavenging arose, followed by predation. Animals went from feeding on microbial mats to feeding on the dead, and then began hunting the living.

The nautilus, however, made it through. No one knows why. At the start of this book I cited a Hawaiian creation myth that judges the octopus a “lone survivor” from an earlier world. The real survivor is indeed a cephalopod, but nautilus rather than octopus. Still living in the Pacific, present-day nautiluses are little changed from 200 million years ago.

Octopuses and other cephalopods have exceptionally good eyes, and these are eyes built on the same general design as ours. Two experiments in the evolution of large nervous systems landed on similar ways of seeing. But the nervous systems beneath those eyes are organized very differently.

But octopuses, far more than rats and pigeons, have their own ideas: “mischief and craft,”

“When you work with fish, they have no idea they are in a tank, somewhere unnatural. With octopuses it is totally different. They know that they are inside this special place, and you are outside it. All their behaviors are affected by their awareness of captivity.”

across the wide range of animal body plans, only three groups contain some species with “complex active bodies.” Those are chordates (like us), arthropods (like insects and crabs), and a small group of mollusks, the cephalopods.

How does an octopus’s brain relate to its arms? Early work, looking at both behavior and anatomy, gave the impression that the arms enjoyed considerable independence. The channel of nerves that leads from each arm back to the central brain seemed pretty slim. Some behavioral studies gave the impression that octopuses did not even track where their own arms might be. As Roger Hanlon and John Messenger put it in their book Cephalopod Behaviour, the arms seemed “curiously divorced” from the brain, at least in the control of basic motions.

Gibson distinguished two different ways of foraging for food. One way is to specialize on a food that requires little manipulation and can be handled the same way in every case. Her example was a frog catching flying insects. She contrasted this with “extractive” foraging, the kind that involves adapting choices to circumstances, removing food from protective shells and casings, and doing so in a flexible and context-sensitive way.

Cuttlefish appear to have a form of rapid eye movement (REM) sleep, like the sleep in which we dream.

The pigeons were trained to do a simple task with one eye masked, then each pigeon was tested on the same task while being forced to use the other eye. In a study using nine birds, eight of them did not show any “inter-ocular transfer” at all.

What about the ninth?

Skepticism is always possible, but a case is being built here. These results do provide support

I like this science

Octopuses, of at least some species, have an opportunistic, exploratory style of interaction with the world. They are curious, embracing novelty, protean in behavior as well as in body. These features are reminiscent of what Stanislas Dehaene associates with consciousness in human mental life. As he says, the demands of novelty jolt us from unconscious routine into conscious reflection.

There is another notable mode of human-cuttlefish interaction, though “interaction” is not quite the right word. Some cuttlefish behave with a level of indifference that is so intense it is hard to describe.

These are both partial cases, unfinished, in a sense, though one should not think of evolution as goal-directed. Evolution is not heading anywhere, not toward us or anyone else. But I can’t resist seeing, in both animals, an unfinished quality. They are both animals with a one-sidedness in their version of the fundamental signaling duality, the interlocking roles of sender and receiver, producer and interpreter. On the baboon side, there’s a soap opera life, frantic and stressful social complexity, and little means to express it. On the cephalopod side, there’s a simpler social life, hence less to say, but such extraordinary things expressed nonetheless.

In other words, this is evidence of parallel evolution of intelligence within the cephalopods. This buttresses the view that it was no accident that complex nervous systems evolved in cephalopods. It’s not something that happened once and was kept on, with variations, in a couple of different lines. Instead there was an expansion of the nervous system within the octopus line, and another one, in parallel, in the other cephalopods.